Woah there...just how are you cleaning this filter? Something does not sound right here at all. Fist of all, with the pump you have, if you change to a sand filter you will far exceed the flow rating for this filter. Also, cartridge filters are simply better.

Now, do you have a cartridge filter or a DE filter that sometimes people call cartridge filters because they also have cartridges in them? Either way they should not need to be cleaned this often - especially with a true cartridge filter. What I suspect is happening is that your pool guy is rinsing the cartridges but not actually cleaning them. Without something to break down the oils on the paper the filter remains mostly plugged. Your pool guy should be soaking the filters overnight in a degreaser and rinsing before reinstalling in the filter. This should be done once seasonally for seasonal pools or twice yearly for year round operations. The system operating pressure is what actually determines when you need to clean but this should give you an idea of what your maintenance schedule should look like.